How the international community responds to human rights in times of conflict has always been an issue when judgments are made about differential levels of culpability for war crimes.

In Iraq, a conflict I covered on the ground between 2003 and 2007, when the Shia death squads first began their campaign of murder there was a widespread resistance among US and UK officials to acknowledge that a problem existed. When they would acknowledge it, some – shamefully – chose to depict it as a natural consequence of the brutality of the Saddam era.

And while it is true that periods of brutality can condition the time that follows, it is not something that should be tolerated.

In Syria, a similar process is visibly occurring. It is not, as some have claimed, that human rights abuses by the Free Syrian Army are not being reported – they are including by this paper's correspondents in the field – it is that in a wider political context, those atrocities have not attracted the same levels of opprobrium as those committed by Bashar al-Assad's regime.

To state the obvious first: the fact is that the Assad regime abuses have been on a far, far wider scale and conducted over a longer period of time. Regime forces have murdered unarmed demonstrators and tortured minors.

The regime has used both indirect and direct fire indiscriminately on civilian centres, amounting to serious war crimes, and has conducted a long-running campaign to terrorise those areas opposed to the regime.

When atrocities attributed to regime forces or militias have emerged they have rightly been condemned by our political leaders and representatives.

But sadly it has also been the case when the Free Syrian Army or its allies, some of them jihadi groups, have committed war crimes and serious human rights abuses, the condemnation has been far less vocal or has sought to mitigate the acts by characterising them as somehow an inevitable by-product of the ugliness of war or somehow the responsibility of the Assad regime itself by being the first to abuse.

The reality, as organisations including both Amnesty and Human Rights Watch have made clear, is that there is no excusing war crimes, whomever commits them.

"It is not," Benedict continued, "about equivalence or saying the scale of abuses is anywhere near the violations by government forces – it is about taking a consistent approach whenever abuses and violations occur and by whomever. The armed opposition do not get a free pass because their opponent is terrorising, punishing and humiliating civilians across Syria."

The murders of the Berri clan members has not been an isolated incident. As an Amnesty statement made clear only days before that event, a growing number of abuses by the FSA had been visible in the weeks before, including "deliberate and unlawful killings" as well as the "torture of captured security force members".

It is true to say that these issues have been debated more thoroughly among members of the Syrian opposition, some of whom are appalled by what they have seen, rather than among some of those western countries have given both political and practical support to Syria's armed opposition, including the US who – it has been persistently reported – has been escalating its assistance.

Both the US state department and Britain's Foreign Office – which recently announced increased support for the rebels – need to be unequivocal in their condemnation of all abuses that are committed and not just those which are the responsibility of the regime, including warning the FSA that there are concrete consequences contingent on both abuses and also the failure of local leaders to act when abuses are committed.

It should be made explicitly clear that murder, kidnapping and torture by the opposition will not only endanger the support that they are currently receiving but that individuals responsible will be pursued and prosecuted for their crimes. Because if humanitarian law is to have any real meaning, it must be applied both thoroughly and evenhandedly – not only to regimes the west disapproves of.